Kinematic Constraints on Mantle-Lithosphere Interactions in Eastern Africa

东非地幔-岩石圈相互作用的运动学制约大陆岩石圈裂解是控制大陆生长演化和洋盆形成的基本过程。它通过控制裂谷盆地及其成功裂陷的对应物被动大陆边缘的油气和热资源的形成，发挥着至关重要的经济作用。大陆裂谷通过热传递和岩浆作用，并可能通过地幔流动对岩石圈变形的力学作用，涉及整个地幔-岩石圈系统。因此，大陆裂谷是研究地球较深和较浅部分之间耦合和交换的主要环境。东非裂谷(EAR)，通常被认为是裂谷和大陆裂解的现代原型，也是目前地球上唯一将大陆全长撕裂的裂谷，为此类研究提供了良好的环境。分析东非裂谷(EAR)中的GPS和地震跳跃矢量数据，结合最近的岩石圈次结构图像和地震各向异性数据，表明地幔流动可能与非洲超羽有关，与坦桑尼亚克拉通200公里厚的岩石圈龙骨相互作用，推动了东非的岩石圈运动和大陆裂谷。这一假设正在通过以下几个方面得到验证：(1)在坦桑尼亚新的和现有的地点使用GPS测量建立耳朵的运动学，(2)通过GPS速度和地震各向异性数据的反演以及从羽流-岩石圈相互作用模型评估软流圈流动，(3)使用建模和‘估计’流动作为边界条件，建立软流圈-岩石圈相互作用的3D有限元模型。这项工作正在解决大陆板块构造的一些基本问题：伸展应变是广泛分布的还是最初局限于狭窄的区域？地幔流场和克拉通龙骨之间的相互作用是否影响大陆板块内应变的局部化和定向？除了这些全球构造问题，我们的工作还将回答以下东非特有的问题：缺乏岩浆的西部裂谷系统的起源是什么？东西部裂谷系之间的联系运动学是什么？

Kinematic constraints on mantle-lithosphere interactions in East AfricaRifting of continental lithosphere is a fundamental process that controls the growth and evolution of continents and the birth of ocean basins. It plays a crucial economical role by controlling the formation of hydrocarbon and thermal resources in rift basins and their successfully rifted counterparts, passive continental margins. Continental rifting involves the entire mantle-lithosphere system through heat transfer and magmatism, and possibly through the mechanical effect of mantle flow on lithospheric deformation. Continental rifts are therefore a prime setting for the study of coupling and exchanges between the deeper and shallower parts of our planet. The East African Rift (EAR), commonly cited as a modern archetype for rifting and continental breakup and the only rift on Earth that is currently splitting a continent over its entire length, provides a prime setting to such studies.Sparse GPS and earthquake skip vector data in the East African Rift (EAR), coupled with recent tomographic images of sub-lithospheric structures and seismic anisotropy data, suggest that mantle flow, possibly associated with the African Superplume, interacts with the 200~km-thick lithospheric keel of the Tanzanian craton, driving lithospheric motions and continental rifting in eastern Africa. This hypothesis is being tested by (1) establishing the kinematics of the EAR using GPS measurements at new and existing sites in Tanzania, (2) assessing asthenospheric flow from an inversion of GPS velocities and seismic anisotropy data and from plume-lithosphere interactions models, (3) using the modeled and ``estimated'' flow as boundary conditions to a 3D finite element model of asthenosphere-lithosphere interactions.This work is addressing some of the fundamental questions of continental plate tectonics: Are extensional strains broadly distributed or initially localized to narrow zones? Do interactions between mantle flow fields and cratonic keels influence the localization and orientation of strain within continental plates? In addition to these global tectonic issues, our work will answer the following questions specific to East Africa: What is the origin of the magma-poor Western rift system? What is the kinematics of linkage between the Western and Eastern rift systems?